1. Field of the Invention
The invention relates to document processing, and to document imaging. The invention further relates to document processing systems of the type in which a large number of documents are rapidly, continuously, and singly transported past one or more imaging cameras.
2. Background Art
A typical document processing system includes a feeder and a separator in the document-feeding portion of the system, and a series of roller pairs or belts in the document-transporting portion of the system. In the feeding portion of the system, the feeder acts with the separator to feed documents singly, in order, from a stack. In the transporting portion of the system, the roller pairs and/or belts convey the documents, one at a time, past other processing devices such as readers, printers, and sorters that perform operations on the documents. The feeder is typically a feed wheel, but may take other forms. The separator may be a wheel, but also may take other forms such as a belt. Further, the components in the transporting portion of the system may take a variety of forms.
In document processors, throughput is measured by the number of items processed in a given time. Accordingly, in the event that poor performance of any components leads to the need to reprocess documents, throughput is degraded.
Banks, credit unions, and other financial institutions use document processing systems to regularly process checks, deposit slips, and other types of bank documents in order to execute financial transactions efficiently. Document processing systems have therefore become quite prevalent in the industry. Typically, information is printed on these documents in magnetic ink which can be read both by the human eye and a computer. This form of printing is read by a process called magnetic ink character recognition (MICR). As part of the recognition process, a MICR magnetic read head is used to read the information printed on the document.
In addition to performing magnetic ink character recognition (MICR) on documents, document processing systems also implement optical character recognition (OCR) on documents. In order to perform optical character recognition (OCR), optical imaging cameras are used to image the passing documents. Further, in some applications, document processing systems capture front and/or rear images of passing documents using one or more image cameras.
In a document processing system wherein a large number of documents are rapidly, continuously, and singly transported past one or more imaging cameras, a major problem for image quality and usability is the build up of paper dust in the optical path of the image cameras. The documents shed paper dust due to frictional forces that are applied to the documents as they are propelled down the transport path.
In a conventional arrangement, the camera views the document through a glass window in the document transport track. This window is recessed back from the inside wall of the document track to avoid contact with documents, and to prevent the leading edge of the document from catching on the front of the window.
This existing arrangement creates a cavity for dust accumulation. This dust build up can be so great in existing document processing systems that it will result in image quality and usability issues. Dust can create streaks in the image which may cause areas of the image to be unreadable by both human operators and optical character recognition (OCR) algorithms. If this dust is allowed to accumulate, it will lead to the degradation of the image and optical character recognition performance of the system. This degradation will lead to expensive reprocessing of documents. In order to avoid reprocessing of documents, operators are currently required to clean the camera glass on a continual basis.